Proton Polarization and the Spin-Orbit Potential

A treatment of proton elastic scattering, valid to first order in the strength of the spin-orbit optical-model potential, shows that this quantity merely serves as a scaling factor for the polarization of the outgoing protons. The angular dependence of the polarization is then determined by the form factor of this potential together with the parameters of the central potential. At small scattering angles, however, only the spin-orbit form factor is important, aside from the well-known Coulomb interaction. Calculations of the proton polarization at various energies from 10 to 20 MeV support these conclusions and indicate that for medium-weight nuclei, the radius parameter of the spin-orbit potential $r_{\mathrm{so}}\approx 1.1$ F instead of 1.3 F, the corresponding value used for the central potential.